Pawl Wear Test, Higher Speed

My original pawl wear test (post of Nov. 16, 2010 ) used a gearmotor that ran at 20 rpm.  The wear pattern on a pawl showed an impression on the flank of the pawl where each ratchet tooth initially made contact, then abrasion on down to the tip and across the tip.  Because there was abrasion across the tip, the pawl was ground down with time and I could quantitatively compare materials by the amount that the pawl was shortened.

A problem with this test is that reel spools do at times spin much faster than 20 rpm, and this might greatly affect wear.  So I have now obtained a faster gearmotor (220 rpm) and re-run the test with a natural Delrin pawl.  Testing time was 15 hours instead of 7 days, in order to get the same number of contacts on the pawl.

This time the wear pattern was different.  The impact line on the flank of the pawl can still be seen, but there is no abrasion on down the flank and across the tip.  So the pawl shows no wear that I can measure.  Apparently the pawl strikes a ratchet tooth and then rebounds sufficiently that there is no more contact with that tooth.  If testing time were continued, the impact impression would likely become larger and there would eventually be complete failure.  But I think that I will have to use this faster tester for qualitative rather than quantitative comparison of materials.

I have also made a fixture (same gearmotor) to allow testing of the new pawl configuration that I am considering.

Where am I going with this?  I am trying to justify the use of a metal pawl (slavery to tradition).  My criteria for a good pawl material are a) corrosion resistance, b) ease of machining, and c) durability.  Obviously plastic is going to win on the first two criteria.  Because I have only tried soft metals, plastic so far wins on the third criteria also.

I have by now been able to machine the new design pawl from 416 stainless, which can be heat treated to improve hardness.  I am also interested in using bronze, which is probably more corrosion resistant than stainless in this application.  There are several bronzes to consider. Expect some future posts on this development.

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3 Responses to Pawl Wear Test, Higher Speed

  1. Leroy Teeple says:

    I have been using Eryalyte, a polyester replacement for brass for the gear and pawl. Like you I struggled with the thought of plastics holding up well as my first reels were made with a steel and then a stainless gear and pawl. They sound nice.

    • dave49 says:

      I think that you mean Ertalyte, a PET formulated for low wear. This had not come to my attention before, and it looks very promising. You have my pawl drawing, can you send me a chip big enough to make one? I would like to test in the manner of the other plastics.
      I see that Professional Plastics has this material in small quantity but there are 2 grades, both unreinforced. PET-P is straight Ertalyte and TX has internal lubricant. Which do you use?

  2. Leroy Teeple says:

    I have some of the TX on order that should be here by the end of the week, up till now I have been using the straight. I will send you a small sample of each when the TX gets here.


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